<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <link rel="stylesheet" href="my.css">
    <style>
        *{
            margin: auto;
        }
    </style>
</head>
<body>
<div class="farther">
    <div class="box1"></div>
    <div class="box2"></div>
    <div class="box3"></div>
</div>
<div class="farther2">
    <div class="box4"></div>
    <div class="box5"></div>
    <div class="box6"></div>
    <div class="box7"></div>
    <div class="box8"></div>
    <div class="box9"></div>
</div>
<div class="farther3"></div>
</body>
</html>